Estimation and characterization of PCDD/Fs and dioxin-like PCBs from secondary copper and aluminum metallurgies in China

Abstract

The secondary metallurgy industry is considered as one source of polychlorinated dibenzo- p-dioxin and dibenzofurans (PCDD/Fs). This study investigated the emission factors and total emissions amounts of PCDD/Fs and dioxin-like polychlorinated biphenyls (dioxin-like PCBs) released from secondary aluminum and copper metallurgy industries in China. The congener patterns are shown and the formation mechanism is also discussed in this paper. The toxic equivalency (TEQ) emission factor of PCDD/Fs is higher for secondary copper production, at 14 802 ng TEQ t −1 than for secondary aluminum production, at 2650 ng TEQ t −1. However, the TEQ emission factor of dioxin-like PCBs of secondary aluminum production, with 193 ng TEQ t −1, is higher than that of secondary copper production with 98.1 ng TEQ t −1. The total estimated emission amount of PCDD/Fs released to air from the production of 2.75 million tons secondary aluminum and 2 million tons secondary copper in 2007 are 7.3 and 37.5 g TEQ yr −1, respectively, the corresponding dioxin-like PCBs total emission amounts being 0.53 and 0.2 g TEQ yr −1 respectively. In general, the emission factors and the total emission amounts of the secondary aluminum and copper metallurgies in China stay in the middle level compared to values reported for other countries. The most abundant congener of PCDD/Fs is 2,3,4,7,8-PeCDF and the most abundant congener of dioxin-like PCBs is CB-126 in samples collected from both secondary aluminum and copper metallurgies. According to the distribution of organochlorocompounds (PCDF > PCDD > PCB, PCDF/PCDD >> 1) and the dominant contribution of higher chlorinated congeners, the de novo synthesis is assumed to be the main formation pathway of PCDD/Fs and PCBs in the secondary copper and aluminum metallurgies.